Process and burner and burner assembly for lpg



April 25, 1967 H. M. KATz ET AL 3,315,725

PROCESS AND BURNER AND BURNER ASSEMBLY FOR LPG Filed Oct. 18, 1965 FIG. 2'

FIG. 5

FIG. 6'

INVENTORS H. MQKATZ R. C. PRYOR ATTORNEYS United States Patent 3,315,725 PROCESS AND BURNER AND BURNER ASSEMBLY FOR LPG Howard M. Katz and Robert C. Pryor, both of Bartlesville, Okla, assignors to Phillips Petroleum Company,

a corporation of Delaware Filed Oct. 18, 1965, Ser. No. 497,055 15 Claims. (Cl. 158-116) This invention relates to a process and burner for burning liquefied normally gaseous hydrocarbons without formation of ice on the burner.

Commercially available burners are not adapted to the burning of LPG at high rates without forming ice on the burner around the orifice(s) thereof which eventually unduly restricts the flow of fuel or cuts it off entirely. In the burning of -liquid propane in a kiln thru which cold rock aggregate is passed to be heated for mixing with hot asphalt in preparing road building material, it was found that the burner orifice(s) became covered with ice which eventually shut off the flow of fuel. The copending application of Robert C. Pryor, S.N. 456,371, filed May 17, 1965, discloses the type of apparatus and process to which the instant invention is applicable. It was in the conversion of this type of process from oil-burning to LPB-burning that the problem was discoverd. In the apparatus and process of said copending application, the liquefied hydrocarbon is fed to the burner under pressure in liquid form and injected into the kiln thru burner nozzles or orifices while passing an annular stream of primary air directly over and around the burner and an annular stream of secondary air outside of the primary air is fed into the combustion zone at a locus substantially downstream of the zone of mixing for the primary air and the vaporized hydrocarbon. The arrangement of apparatus disclosed in said application projects the combustion zone substantially downstream of the burner and the moisture in the combustion air contacts the face of the burner immediately surrounding the orifices or injection point of the fuel. In this situation, if the injected fuel is allowed to vaporize within the orifices of the burner, suflicient refrigeration is created to freeze the moisture in the refrigerated area immediately surrounding the orifice and the ice builds up so as to shut off fuel flow.

This invention provides a burner and process for combusting liquefied normally gaseous hydrocarbon material such as propane, butane, and liquefied natural gas components without causing ice to form on the face of the burner.

Accordingly, it is an object of the invention to provide an improved burner and process for burning liquefied normally gaseous hydrocarbons in a combustion zone downstream of the burner which avoids freeze-up of moisture in the combustion air. Another object is to provide an improved burner for combusting normally gaseous liquefied hydrocarbons in a combustion zone substantially downstream from the burner. Other objects of the invention will become apparent to one skilled in the art upon consideration of the accompanying disclosure.

A broad aspect of the invention comprises a burner having a hollow body member forming an axial fuel duct or passageway and having a burner face which recedes from a plane normal to the burner axis at the intersection of the face with said axis, and at least one orifice communicating with the fuel duct thru said face comprising a cylindrical conduit of a maximum length of A" and a diameter in the range of to Processwise, the invention comprises burning liquefied normally gaseous hydrocarbons downstream of a burner provided with an orifice with combustion air which contains moisture, comprising supplying the liquid hydrocarbon to said burner in liquid form at a pressure substantially in excess of the vaporization pressure thereof, passing said liquid hydrocarbon thru said orifice while maintaining the pressure drop across said orifice not in excess of the aforesaid excess pressure over vaporization pressure so as to avoid any substantial vaporization of the hydrocarbon within the orifice with attendant freezing of moisture on the burner, and vaporizing and burning the vaporized hydrocarbon substantially downstream of the burner. The vaporized hydrocarbon is mixed with an annular stream of primary air flowing directly over the burner, and farther downstream, with an annular stream of secondary air.

It has been found that the critical feature of a burner for burning liquefied normally gaseous petroleum substantially downstream of the burner with combustion air containing moisture lies in the length of the orifice thu which the fuel is dispersed, jetted, or injected into the combustion zone. When utilizing an orifice length exceeding A3" where the diameter of the orifice is in the range of A to the pressure drop across the orifice is sufficient to allow some vaporization of the liquid fuel within the downstream end of the orifice and the resulting refrigeration effect lowers the temperature of the metal surrounding the orifice substantially below the freezing temperature of water and causes the moisture in the combustion air to freeze on the burner face around the burner orifice.

A more complete understanding of the invention may be had by reference to the accompanying schematic drawing of which FIGURE 1 is a longitudinal cross-section of a burner made in accordance with the invention; FIG- URE 2 is a plan view of the burner of FIGURE 1; FIGURE 3 is a longitudinal cross section of a burner made in accordance with another aspect of the invention; FIGURE 4 is a plan view of the face of the burner of FIGURE 3; FIGURE 5 is a longitudinal cross sectional view of an orifice tip for use in the burner of FIGURES 3 and 4; and FIGURE 6 is a fragmentary view of a burner face or orifice tip illustrating another orifice configuration.

Referring to FIGURES l and 2, burner 10 comprises a hollow burner body 12 having a cylindrical bore 14 and provided with threads 16 or other suitable means for attaching the burner to a fuel tube or conduit 17 which connects with a high pressure LP gas fuel tank 19. Burner body 12 is provided with an arcuate face 18 which is hemispheroidal but may take the form of a lesser section of a sphere, as any spherical section cut ofi by a plane intersecting a sphere. One or more orifices are formed in the face of the burner, such as 7, including axial orifice 2t) and orifices 22 disposed in a ring concentric with the burner axis and axial orifice.

The orifices are preferably formed by drilling a hole having a diameter in the range of to A and limiting the length of the hole to a maximum of /s" by countersin'king the outer end of the hole by drilling on the same axis with a larger bit or a countersink bit. The walls of the countersunk or outwardly flared section 24 adjoining drill hole 26 form an angle of about 15 to with the axis or an included angle in the range of about 30 to 15. The length of the flared or countersunk section of the orifice may range from 0 to about Ring orifices 22 are symmetrically positioned and the axes thereof preferably intersect at a common point on the axis of the burner body. The angle formed by the axes of the ring orifices and the burner axis is in the range of 30 to Referring to FIGURES 3 and 4 burner head 30 is of circular transverse cross section. Burner body 32 is pro,

vided with an axial bore 34 and a plurality of individual bores 36 leading to the several ports of the burner including axial port 38 and ring ports 40 all of which are threaded for receipt of an orifice member such as that shown in FIGURES and 6. The arrangement of ports may be the same as the arrangement of orifices in FIGURES 1 and 2. Burner face 42 is arcuate circumferentially and flat or straight radially. However, the face of burner body 32 may also be arcuate radially as in a spheroidal section and the axes of burners 36 and ports 40 are normal to the face of the burner. The inlet end of bore 34 is threaded as at 44 to provide attaching means for connecting with a liquid fuel supply conduit.

Burner body 32 may be of any suitable size. In the burner illustrated in FIGURES 3 and 4, the burner body has a maximum diameter of 5", the face of the burner around port 38 perpendicular to the axis has a diameter of 1", bore 34 has a diameter of %1, and bores 36 are /2 diameter. Face 42 forms an angle of 60 with the burner axis and the cylindrical section 46 of the burner body has a length of about /2". The cylindrical inlet section 48 has a length of about 1" and flared section 50 forms an angle of about 30 with the burner axis.

Referring to FIGURE 5, individual burner 60 comprises a burner body member 62 having axial bore 64 converging at its downstream end into cylindrical orifice 66 thru a tapered section 68 formed by the end of the drill utilized in drilling bore 64. Outwardly and radially flared section 70 at the downstream end of hole 66 is also formed by countersinking or drilling to control the length of cylindrical passageway 66 at a maximum of /8. The orifice 66 of burner body 6-2 conforms to the requirements disclosed for the orifices of the burner of FIGURES l and 2. The inlet end of burner body 62 is provided with a threaded section 72. The face 74 of the burner body is in the form of a section of a sphere. In the application of this burner tip to the burner body of FIGURES 3 and 4, burner face 74 has a radius of /2 and the center of this sphere is on the axis of bore 64. Bore 64- has a diameter of /8" and threads 72 are /2" tapered threads to be threaded into ports 38 and 40 of burner body 32. Cylindrical orifice 66 has a length of about A5" and the flared wall of 70 is also about /s" in length.

Referring to FIGURE 6, the face of the orifice tip or burner body 80 has a thickness of /8" and orifice 82 is simply a drilled hole having a diameter in the range of to axially or radially thru the face of the orifice tip or burner face. This construction is applicable to either the burner tip of FIGURE 5 or the burner body of FIGURES 1 and 2.

The faces of the burner body of FIGURES 1 and 2 and the orifice tip of FIGURE 5 are highly polished to minimize the tendency for deposition of ice thereon and it is also preferable to polish the inside of the orifice passageways so as to provide better flow of fuel.

When utilizing a plurality of orifices either in the burner body of FIGURES 1 and 2 or in that of FIGURES 3 and 4, it is generally preferred to use an axial orifice of larger diameter than the diameters of the ring orifices. A table of hole diameters in different orifice sets together with the maximum flow rate thru the orifices is set forth in the table below:

In operation of the burner in accordance with the invention, it is essential to maintain pressure at the orifice substantially above 20 p.s.i.g. at the inlet to the cylindrical orifice section to not more than 20 p.s.i.g. at the outlet end of this section. Suitable pressure in the liquid fuel system is maintained by means of a pump in the fuel supply line between the LPG tank and the burner (not shown), there being a recycle or bypass line to the supply tank from downstream of the pump.

When utilizing such a pressure differential at a burner orifice in the size range disclosed having a length not exceeding A5", freezing of moisture on the face of the burner or orifice tip is avoided or minimized to such an extent that there is no interference with fuel flow and dispersion. In addition to the advantage of prevention of freeze-up, the burner orifice constructed in accordance with the invention provides excellent flow control.

The burner and orifice structure not only provides good flow characteristics and avoids freeze-up but also provides excellent turn-down. To illustrate, with the arrangement of orifices in set number 1 of the above table it is feasible to turn down the burner from a maximum flow of 28 liquid g.p.m. to about 3 g.p.m. (gallons per minute).

Certain modifications of the invention will become apparent to those skilled in the art and the illustrative details disclosed are not to be construed as imposing unnecessary limitations on the invention.

We claim:

1. A burner for use in burning liquefied normally gaseous hydrocarbons which comprises:

(1) a hollow body member providing an axial fuel passageway and having a convex face at the downstream end and means at the opposite end for attaching to a fuel conduit;

(2) at least one orifice communicating with said fuel passageway thru said face, said orifice comprising a cylindrical hole having a maximum length of /3 inch and a diameter in the range of to inch, when only one orifice, same being axially disposed; an

(3) a source of high pressure liquefied petroleum gas connected by a fuel conduit with the means of (l).

2. The burner of claim 1 wherein the wall of said burner forming said face is of a thickness greater than 4; inch, said hole is in said wall, and said hole length is attained by forming a frusto-conical passageway at one end'of said hole coaxial therewith and flaring outwardly directly from the periphery of said hole.

3. The burner of claim 2 wherein said frusto-conical passageway is in said face at the downstream end of said 4. The burner of claim 1 including a plurality of said orifices symmetrically positioned on said face in a ring concentric with said axial orifice, the axes thereof forming an angle with the axis of said burner and said orifice in the range of 30 to 5. The burner of claim 4 wherein the downstream end of each said orifice adjoins the small end of a fr-ustoconical coaxial opening,'the diameter of said small end being the same as that of said hole and the included angle of said opening being in the range of about 30 to 6. A burner for use in burning liquefied normally gaseous hydrocarbons which comprises:

(1) a hollow body member forming an axial fuel duct of substantially larger cross-sectional area than that of the orifice of (2) below, said member having a downstream face receding from a plane normal to the burner axis at the intersection of said face with said axis and means at the upstream end for attaching to a fuel supply line;

(2) at least one orifice communicating with said fuel duct thru said face comprising a cylindrical conduit having a length in the range of to /8 inch and a diameter in the range of 7 to inch, when only one orifice, said orifice being axially positioned; and

(3) a source of high pressure liquefied petroleum gas connected by a fuel line with the means of (1).

7. The burner of claim 6 including an axially disposed orifice and .a ring of orifices symmetrically surrounding said axial orifice, the axes thereof having a common point of intersection on the axis of said burner.

8. The burner of claim 7 wherein said orifices are formed in said face and terminate in the downstream end in an outwardly flared frusto-conical opening flaring outwardly directly from the periphery of its orifice, and wherein the burner bore upstream of the orifices is unobstructed and of substantially larger diameter than said orifices.

9. The burner of claim 6 wherein said orifice is positioned in an orifice tip detachably inserted in said face.

10. The burner of claim 6 including a ring of threaded ports symmetrically disposed in said face around an axial threaded port and an orifice ti-p threaded into each said port having a relatively large diameter axial bore communicating with said fuel duct and terminating at the downstream end in said orfiice of (2), the axes of said ring ports, said bores, and said orifices having a comm-on point of intersection with the burner axis.

11. The burner of claim wherein the angle between the burner axis and the axes of said ring orifices is in the range of about 30 to 90.

12. The burner of claim 10 wherein the diameter of said axial orifice is in the range of to inch larger than the diameter of the orifices in the ring tips.

13. The burner of claim 6 wherein the downstream end of said cylindrical conduit adjoins the small end of a frusto-conical coaxial opening, the diameter of said small end being equal to the diameter of said conduit.

14. A process for burning liquefied petroleum gas in an ambient containing moisture adjacent a burner provided with a cylindrical orifice which normally freezes on said burner around said orifice due to vaporization of liquefied petroleum in said orifice with attendant refrigeration which process comprises the steps of:

(1) supplying said liquefied petroleum in said burner at a pressure substantially in excess of the vaporization pressure thereof;

(2) maintaining the length of said orifice in the range of to 4; inch and its diameter in the range f to 7 inch and maintaining fluid pressure drop across said orifice not in excess of the excess pressure of step (1);

(3) flowing said liquefied hydrocarbon thru the orifice of step (2) principally in liquid form and vaporizing same downstream of said orifice; and

(4) mixing oxygen-containing gas with the vaporized hydrocarbon under combustion conditions so as to burn same.

15. The process of claim 14 wherein the liquid pressure at said orifice is maintained substantially above 20 p.s.i.gv at the inlet thereof to not more than 20 p.s.i.g. at the outlet.

References Cited by the Examiner UNITED STATES PATENTS 1,364,972 1/1921 Andersone et al. 158-33 1,763,289 6/1930 Anderson et al 15833 2,086,074 7/1937 Genovese. 2,618,928 11/1952 Nathan 158-76 X 2,815,019 12/1957 Keible. 2,948,478 8/ 1960 Walsh.

JAMES W. WESTHAVER, Primary Examiner. 

1. A BURNER FOR USE IN BURNING LIQUEFIED NORMALLY GASEOUS HYDROCARBONS WHICH COMPRISES: (1) A HOLLOW BODY MEMBER PROVIDING AN AXIAL FUEL PASSAGEWAY AND HAVING A CONVEX FACE AT THE DOWNSTREAM END AND MEANS AT THE OPPOSITE END FOR ATTCHING TO A FUEL CONDUIT; (2) AT LEAST ONE ORIFICE COMMUNICATING WITH SAID FUEL PASSAGEWAY THRU SAID FACE, SAID ORIFICE COMPRISING A CYLINDRICAL HOLE HAVING A MAXIMUM LENGTH OF 1/8 INCH AND A DIAMETER IN THE RANGE OF 1/32 TO 5/16 INCH, 